Using first-principles total-energy calculations within the hybrid full-potential augmented plane-wave plus local orbitals (APW+1o) method, we have investigated the structural and electronic properties of PbSxTe1-x and PbSexTe1-x alloys. In this study we employ two exchange and correlation approximations, the local-density (LDA) and generalized gradient (GGA) approximations. Equilibrium volumes, bulk moduli, charge densities, density of states and band structures of lead chalcogenide alloys, in the rocksalt structure are presented. The results show that both ternary alloys possess a direct and smaller energy gap comparing with binary compounds studied. A model structure of 32-atoms supercell is used. (C) 2008 Published by Elsevier B.V.